This invention relates generally to injection molding and more particularly to an improved injection molding probe.
Heated injection molding nozzles and probes are widely used to maintain pressurized melt at a uniform temperature as it flows towards a gate leading to a cavity. The difference between a nozzle and a probe is that the melt flows through a nozzle and around a probe. Previously, as seen in U.S. Pat. No. 4,820,147 to Gellert which issued Apr. 11, 1989 and Gellert Canadian patent application serial number 2,032,728-6 filed Dec. 19, 1990 entitled "Injection Molding Probe With Varying Heat Profile", probes had an electrical heating element which ran longitudinally in the outer body of the probe. However, they do show the heating element bent back upon itself in different sections to provide varying heat along the length of the probe to compensate for differences in heat loss due to the structure of the probe. U.S. Pat. No. 4,557,685 to Gellert which issued Dec. 10, 1985 shows a similar provision for nozzles by varying the pitch of the helical heating element which is wound around the outer surface of the nozzle body.
It is also well known to mount removable thermocouples in probes to monitor the operating temperature near the forward end of the probe. An early example is seen in U.S. Pat. No. 4,611,394 to Gellert which issued Sep. 16, 1986 and shows a thermocouple extending to the forward end of the probe through a sleeve extending longitudinally beside a central cartridge heater. More recently, Gellert U.S. Pat. No. 5,122,050 which issued Jun. 16, 1992 entitled "Injection Molding Probe With a Longitudinal Thermocouple Bore and Off Center Heating Element" shows shifting the heating element off center to accommodate a longitudinal thermocouple bore without unduly increasing the outer diameter of the body of the probe. All of these previous arrangements having both a longitudinal thermocouple bore and a heating element have the disadvantage that either one or both of them must be off center. Also in order to have sufficient strength, the outer diameter of the probe was increased to compensate for the distance provided between the thermocouple bore and the heating element.